"He admits that he murdered these two men; that he used drugs and alcohol that morning; and that he knew what he was doing was wrong," Erath County District Attorney Alan Nash told jurors in his opening statement.

Nash said Routh confessed after the murders. Then the DA detailed the shootings.

Chad Littlefield was shot four times in the back, in the hand, the face and top of his head. Chad Littlefield was killed with a 9mm weapon; Chris Kyle with a .45-caliber.

"Five times in the back and side; one time in the side of the head," Nash said.

He said Routh was in a psychotic state when Kyle and Littlefield were killed on February 2, 2013 at an Erath County gun range. In Routh's mind, it was kill or be killed.

The defense lawyer told jurors that Kyle and Littlefield grew so concerned about Routh's mental state that they exchanged texts as they sat next to each other on the way to the range. Routh was with them inside Kyle's pickup truck.

Moore quoted from the texts: "This dude is straight up nuts," Kyle wrote.